The present invention relates to a switch valve arrangment for changing over the inlet of a fluid pressure slave unit from the outlet of a first fluid pressure generator to the outlet of a second fluid pressure generator during switch-on of the second fluid pressure generator. For brake systems of automotive vehicles, the arrangement comprises a first valve which, during switch-on of the second fluid pressure generator, blocks the connection between the first fluid pressure generator and the fluid pressure slave unit. The arrangement further comprising a second valve releasing the connection between the second fluid pressure generator and the fluid pressure slave unit during switch-on of the second fluid pressure generator.
A switch valve arrangement of this type is described in German Patent Application No. P 35 04 562.0, wherein the first valve is a hydraulically operable 2-way/2-position valve which, in non-actuated condition, takes a passage position and connects the one working chamber forming the first fluid pressure generator of a tandem master brake cylinder of an anti-blocking brake system for automotive vehicles to wheel brakes of the automotive vehicle. In the working position of the 2-way/2-position valve, a check valve is operative within the 2-way/2-position valve such that a fluid pressure flow from the working chamber of the tandem master cylinder to the wheel brakes is precluded. The second valve of the valve arrangement is a check valve separated from the first check valve which, by way of a magnetic valve formed as a switch valve, is connected to the working chamber of a hydraulic brake force booster provided upstream of the tandem master brake cylinder. The magnetic valve is switched over by a slip monitoring electronic system such that the connection between brake force booster and check valve is established as soon as the monitoring electronic system has detected a slip condition in a decelerated vehicle wheel. The outlet of the magnetic valve, moreover, is directly connected to a control inlet of the first valve. Magnetic valve and brake force booster can be regarded as a second fluid pressure generator switching-on of which causes the first valve to be controlled into its blocking position and the second valve to be opened such that the output fluid pressure of the magnetic valve is then applied to the wheel brakes, the brakes will fail.
It is an object of the present invention to provide a switch valve arrangement of the described type which, with the second fluid pressure generator in the switched-on condition and a output circuit break, precludes egress of pressure fluid from the second fluid pressure generator.